The hadoop s3guard import command can list and import a bucket's metadata into a S3Guard table. This is harmless if the contents are already imported.

hadoop s3guard import s3a://guarded-table/

2018-05-31 15:47:45,672 [main] INFO s3guard.S3GuardTool (S3GuardTool.java:initMetadataStore(270)) -
    Metadata store DynamoDBMetadataStore{region=eu-west-1, tableName=guarded-table} is initialized.
Inserted 0 items into Metadata Store

You do not need to issue this command after creating a table; the data is added as listings of S3 paths find new entries. It merely saves by proactively building up the database.